Through the studies proposed in this project we hope to: a) help provide a more comprehensive understanding of how the acinar cell of the pancreas secretes its particular mixture of proteins, the digestive enzymes; b) describe the kinetics of digestive enzyme transport in greater detail; c) continue to test the hypothesis that these protein molecules cross specialized biological membranes by passing through them; d) seek evidence for and compare various potential mechanisms for the monomolecular transport of proteins through membranes; e) learn about the nature and potential biological significance of the enteropancreatic circulation of digestive enzyme; and f) learn about the nature and potential biological signficance of the endocrine secretion of digestive enzyme. We will attempt to achieve these goals using a variety of experimental approaches drawn from transport physiology, biophysics, biochemistry, and cell biology.